Emergent installation for drilling and production at great depth at sea

ABSTRACT

AN EMERGENT DRILLING AND PRODUCTION INSTALLATION FOR OPERATING AT GREAT DEPTHS AT SEA, ESPECIALLY FOR THE PRODUCTION OF HYDROCARBONS FROM A FIELD UNDER THE SEA-BED, COMPRISING THE COMBINATION OF AN OSCILLATING COLUMN HAVING A POSITIVE BUOYANCY, SUPPORTING AT ITS UPPER PORTION A DRILLING AND PRODUCTION PLATFORM AND ARTICULATED AT ITS LOWER PORTION, WITH TWO DEGREES OF FREEDOM, ON A BASE HAVING A HIGH POSITIVE BUOYANCY AND FIXED TO THE SEA-BED AT A PRE-DETERMINED DISTANCE THEREFROM BY ANCHORAGE MEMBERS UNDER TENSION DRIVEN AND CEMENTED INTO THE SEA-BED. THE OSCILLATING COLUMN MAY BE PROVIDED WITH INTERNAL STORAGE COMPARTMENTS FOR RECEIVING PART OF THE PRODUCTS OBTAINED.

M. LAFFONT Dec. 14, 1971 3,626,701 EMERGENT INSTALLATION FOR DRILLINGAND PRODUCTION AT GREAT DEPTH AT SEA 8 Sheets-Sheet 1 Filed March 26,1970 Dec. 14, 1971 M. LAFFONT 3,626,701

EMERGENT INSTALLATION FOR DRILLING AND PRODUCTION AT GREAT DEPTH AT SEAFiled March 26, 1970 8 Sheets-Sheet 8 Dec. 14, 1971 LAFFONT 3,626,701

EMERGENT INSTALLATION FOR DRILLING AND PRODUCTION AT GREAT DEPTH AT SEAFiled March 26, 1970 8 Sheets-Sheet 5 Ffg74 Dec. 14, 1971 M. LAFFONT3,626,701

EMERGENT INSTALLATION FOR DRILLING AND PRODUCTION AT GREAT DEPTH AT SEAFiled March 26, 1970 Sheets-Sheet A 1971 M. LAFFONT Q 3,626,

EMERGENT INSTALLATION FOR DRILLING AND PRODUCTION AT GREAT DEPTH AT SEAFiled March 26, 1970 8 Sheets-Sheet 5 Dec. 14, 1971 M. LAFFONT 3,626,701

LMERGENT INSTALLATION FOR DRILLING AND PRODUCTION AT GREAT DEPTH AT SEAFiled March 26, 1970 8 Sheets-Sheet 6 7/ s4 54 44 L L- -6-] 6 J Dec. 14,1971' M. LAFFONT 3,626,701

EMBRGENT INSTALLATION FOR DRILLING AND PRODUCTION AT GREAT DEPTH AT SEAFiled March 26, 1970 8 Sheets-Sheet 7 Dec. 14, 1971 M. LAFFONT 3,626,701

EMERGENT INSTALLATION FOR DRILLING AND PRODUCTION AT GREAT DEPTH AT SEAFiled March 26, 1970 8 Sheets-Sheet 8 F2 II can 105 o O O United StatesPatent Int. Cl. E02b 17 /00; E21b 43/ 01 US. Cl. 61-465 5 ClaimsABSTRACT OF THE DISCLOSURE An emergent drilling and productioninstallation for operating at great depths at sea, especially for theproduction of hydrocarbons from a field under the sea-bed, comprisingthe combination of an oscillating column having a positive buoyancy,supporting at its upper portion a drilling and production platform andarticulated at its lower portion, with two degrees of freedom, on a basehaving a high positive buoyancy and fixed to the sea-bed at apre-determined distance therefrom by anchorage members under tensiondriven and cemented into the sea-bed. The oscillating column may beprovided with internal storage compartments for receiving part of theproducts obtained.

The invention relates to an emergent installation for drilling andproduction at great depth at sea, supported on an immersed structuremaintained in a fixed position with respect to the sea-bed.

So-called oscillating platforms are already known, which are supportedon an articulated column by a member giving two degrees of freedom on abase placed on the bottom of the sea; the column has a positive buoyancycreated by floats arranged at its upper portion. Units of this kind aredescribed in French Patent No. 1,519,891 and in the Review Science etVie (February 1969, page 120); they may be utilized for drilling workand also for the production or even the storage of hydrocarbons, forexample. However, the normal application of these platforms is limitedto sea depths of a few hundred metres.

The present invention enables the difliculties encountered in deep waterto be overcome, and provides emer gent drilling and productioninstallations which can be utilized at depths of more than 400 metres.

A drilling and production installation at great depths at sea accordingto the invention is characterized by the combination of a column withpositive buoyancy supporting at its upper portion a drilling andproduction platform, articulated at its lower portion with two degreesof freedom on a base with high positive buoyancy, which is fixed to thesea bottom by traction elements having a length such that thearticulation of the column on the base is maintained under tension.

According to one characteristic feature of the invention, the positivebuoyancy of the base is very much higher than the maximum load which itis capable of receiving at any moment.

According to another characteristic feature of the invention, the basewith positive buoyancy is coupled to the sea-bed, while remaining at afixed distance from this latter, by means of a plurality of piles whichare kept under tension by the force due to the positive buoyancy of thechamber.

Following a further characteristic feature of the inven- 3,626,701Patented Dec. 14, 1971 tion, the pull applied by the piles on the baseis adjusted by the buoyancy given to the said base, thus ensuringrelative stability of the base about its theoretical position.

The invention will be better understood from the description whichfollows below of one example of construction of the installationaccording to the invention, reference being made to the accompanyingdrawings, in which:

FIG. 1 shows a diagrammatic view of the whole installation;

FIG. 2 illustrates the lowering of the base to the desired depth in thesea;

FIG. 3 shows the placing in position of a service boat above the basefor the purpose of fixing the said base;

FIG. 4 shows the lowering of a tube for fixing the base;

FIG. 5 illustrates the drilling of a centering hole for a tube intendedfor anchoring the base;

FIG. 6 shows an anchorage tube placed in position, and its coupling tothe base of the platform;

FIG. 7 represents a vertical cross-section of the base when it has beenplaced in position;

FIG. 8 shows a view looking on the top of the base, illustrating ajunction device between the base and the articulation element fixed tothe foot of the oscillating column;

FIG. 9 shows the assembly of the base and the column after they havebeen coupled together;

FIG. 10 shows a utilization of this platform for drilling operations;

FIG. 11 shows a utilization of this platform for the storage ofhydrocarbons.

In FIG. 1, there has been shown at 1 a base, preferably of meal, whichis constituted by a chamber, the interior of which can be kept under airpressure. At 2 there has been shown the plinth supporting thearticulation element 3 which coupled the whole of the base and the fixedsupport of the articulation element 3 to the column 4. This column isprovided with floats 5 so as to give it at the same time a positivebuoyancy and a restoring couple permitting its stabilization about amean vertical position.

At 6 is shown the platform which is adapted to receive, above thesurface of the water, all the equipments necessary for drilling andproduction. In particular, there is shown at 7 a drilling derrick whichsupports a train of rods 8. This train of rods is engaged in a tube 9rigidly fixed to the base, and is engaged at 11 in the sea-bed shown at12. There has also been shown at 10 a second tube coupling the base 1 tothe sea-bed at a second point.

The base 1 is given a high positive buoyancy. It is held in position bya certain number of tubes such as 9 and 10, which are anchored to thesea-bed 12 and are subjected to a tensile force in consequence of thepositive buoyancy of the base 1.

The chamber is thus stabilized. In fact, it is only affected by the seacurrents, the effect of the swell being very small at the depth ofimmersion, which is of the order of to 400 metres. The base is thus in afixed position, and the oscillating column 4, 5, 6 which is alsosubjected to a positive buoyancy by means of the floats 5, only appliestensile forces to this base, at least during normal use. A supportingforce is applied by the column 4 on the base 1 at the moment ofimmersion of the column 4, in order to permit the plinth 2 carrying thearticulation element to be locked on the base 1.

FIG. 2 illustrates the placing in position of the base 17. For thispurpose, the base having a large positive buoyancy is brought to theplace of immersion by towing.

The base is then lowered by giving it a fairly small negative buoyancywhich is compensated by the positive buoyancy of a series of floats 16a,16g, which are immersed successively. These floats are connected by aline 1 4 to a boat 13.

In order to guide the downward movement of the base 17, there isemployed a series of mooring cables 18 and 19, connected to floatingbodies 20 and 21 which are in turn coupled by anchor chains 22 and 23 toanchors 24 and 25 which are engaged in the sea-bed 26. The immersion ofthe base, which has been previously provided with one or a number ofchains of floats, is also carried out when its buoyancy is slightlynegative. The whole assembly being in equilibrium, the first float isfilled in order to annul its buoyancy, which enables the base to belowered to a certain depth. The various floats are then successivelyimmersed, which permits the lowering of the base to be controlled in avery precise manner and permits its stabilization very exactly at aknown depth.

FIG. 3 shows the base 27 after it has been put in position and suspendedfrom the chain of floats 28. There is then brought above the position ofimmersion, a floating platform equipped for drilling and boringoperations. This platform is shown at 31 and carries a drilling derrick30. The boat which has been employed during the immersion operations isshown at 29. It is connected by a cable to the chain of floats 28 whichsupports the base 27.

Following one of the methods contemplated for fixing the base to thebottom, there have been shown in FIG. 4 at 32, two suspension cableswhich support a column of tubes 37 provided at its upper portion with afloat 34 having a positive buoyancy. On these cables 32 there is fixed aguiding stirrup 33 provided with an opening at its central portion.Through this opening there is lowered a train of drilling rods 36provided at its lower portion with an ultra-sonic transmitter-receiverdevice 39. The column of tubes 37 is first lowered from the surface to adepth slightly greater than the depth of immersion of the base 35, afterwhich the train of rods 36 is lowered. By means of the ultra-sonicdevice and using orientatable jets of fluid, this train of rods can beguided and passed through one of the openings a formed on the peripheryof the base 35. The train of tubes 37 can then be engaged in the sameopening 35a, this opening having a diameter slightly greater than thatof the tubes 37.

The train of rods 36 is then lowered until its lower extremity is incontact with the sea-bed. Three ultra-sonic transmitters havingpre-determined frequencies have previously been prepared. By means ofthe transmitter-receiver, it is possible to know the position of theextremity of the train of rods with respect to the ultra-sonictransmitters. A similar method is described in French Pat. No.1,417,248. By means of a fluid-jet piloting device, the extremity of thetrain of rods can be guided so as to bring it into a previouslydetermined position.

When this operation has been completed and the column of tubes placed inposition, the train of rods is withdrawn and a drilling tool is thenfitted on its extremity.

In FIG. 5, the train of drilling rods provided with a boring tool 41 hasbeen lowered, and there is drilled at the extremity of the column oftubes a pilot hole, as shown, in the sea-bed 38. When this pilot holehas been drilled, a widening tool is employed to increase the diametersufficiently to be able to introduce the column of tubes into it and tocement the column in position.

The cementing operation is shown in FIG. 6. In addition to the twoprevious figures, the cement is shown at 42, permitting the anchorage ofthe train of tubes 37. After blowing out the chamber of the base, thelatter has a positive buoyancy and is held against the lower surface ofthe floats 34.

The above operation is carried out a certain number of times, therebypermitting a series of columns of tubes to be placed in the periphery ofthe base, the various columns being arranged parallel to each other.There is thus available a base which is fixed to the sea-bed by a seriesof tubes which are distributed as uniformly as possible. The base isthus fixed to the sea-bed by means of a series of 20 or 40 tubes forexample, having a diameter of 250 to 500 mm. As these tubes are stronglyanchored to the sea-bed, they can withstand a considerable tensileforce, this force being obtained by giving the base a large positivebuoyancy by driving out the water which partly filled the internal spaceof the base, by means of compressed-air injected from the surface.

FIG. 7 shows the detail of the base when it has been placed in position.

At 43 is shown the body of the base, which is a chamher into which watercan be introduced so as to give it a very low apparent weight, afterwhich this water may be expelled by compressed-air brought from thesurface so as to give the base a large positive buoyancy. This base isheld in position by tubes such as 44, installed in the manner indicatedabove. These tubes are provided at their upper portion with floats 45which serve at the same time as floats for the adjustment of the weightof the column of tubes and as fixing members between the upper part ofthe column of tubes and the upper face of the base. At 46 there havebeen shown guides intended to facilitate subsequent operations forplacing in position a production well-head.

At 47 is shown a petroleum well tubing which passes through the columnof tubes 44. In fact, through the interior of tubes of large size,petroleum wells may be drilled, and the boring may for example be carredout in deviation, starting from the point of entry into the sea-bed. Theanchorage tubes may also be separate from the well tubes.

The tubes are connected to a well-head 48. The production conduit 49connects the well-head 48 to a flexible coupling 50 which is fixed onthe one hand to the production conduit fixed rigidly on the base, and onthe other hand to a tube 51 rigidly fixed to the column of oscillatingplatform 52.

This oscillating platform is articulated on the base 43. The lower partof the oscillating platform supports a first block 53 which can rotateabout an axis formed by two trunnions 54 which are engaged in theportion 52. The block 53 is provided with two trunnions located on aperpendicular axis which is not shown in the drawing.

These trunnions are engaged in two parallel parts 55 supported by thecolumn foot 66. This column foot is engaged at the moment when thecolumn is placed in position on the base in a certain number of fixingdevices 57.

In one possible form of construction, the column foot is provided on itsperiphery with a certain number of jacks 75. The sliding shafts of thesejacks are passed into the column foot during the lowering of thislatter. By applying pressure to the jacks, the sliding rods 75 aredisengaged and come into position in housings provided for that purposein a member 65 rigidly fixed on the base.

The fixing of the oscillating platform to the base is effected bylocking with the jacks 75 and by guides 57 of the column foot 66 withthe support 65 carried by the base.

There can be seen in the assembly, the base 43 having a positivebuoyancy and held in position by the forces applied to the series oftubes 44 anchored to the bottom of the sea. This base supports theoscillating platform through the intermediary of the coupling. Thisplatform has a slight negative buoyancy at the moment when it is placedin position. However, as soon as this operation is completed, the wateris expelled from the floats of the oscillating platform, thus giving ita high positive buoyancy, greater than the load which the platform isintended to carry.

The base is subjected to the effects of sea currents, but the swell onlyproduces limited forces at the level of the base.

On the other hand, the oscillating platform follows the movements due tothe swell and surge of the sea.

The assembly of the base and the oscillating platform is given apositive buoyancy greater than the maximum load which can be applied onthe platform. This assembly is articulated at the level of the upperface of the base.

The depth of use of an assembly of this kind may reach 1,000 metres ofeven more. The assembly can also be utilized at relatively shallowdepths of the order of about a hundred metres, although for shallowdepths the 'advantage of this assembly is less.

FIG. 8 shows a plan view of the junction between the base and theoscillating platform. The base has been shown at 60 and in this case isof cylindrical shape, although bases of rectangular shape may beemployed. In the vicinity of the periphery of this base are shown aseries of tubes serving to fix the said base. There is indicated at 61 atube of small diameter, essentially employed for fixing the base on thesea-bed, the contact surface between the fixing device of the tube 61and the upper face of the base being shown at 62. At 44 there is alsoshown a tube of large diameter, the internal space of which can beemployed for the passage of a tool or a production column. The junctionof this tube and the base is shown at 64. As a result of its positivebuoyancy, the base applies a support against this surface, which isconstituted by a shoulder on the outer part of the tube 63.

There has been shown at 65 a mechanical member rigidly fixed on the baseand secured to the central portion of this latter. This member 65comprises a central recess of rectangular shape and housings 76 intendedto receive jack pistons, as will be explained later.

The foot of the oscillating column has been shown at 66. This foot has acomplementary shape to the recess of the member 65 and can be engaged inthis recess. For the purpose of correct positioning of this column foot,the member 65 is provided with a certain number of guiding elements 73.The column foot 66 has two lugs 67, eachof which receives a trunnion 68rigidly fixed to a working member 53. In a direction perpendicular tothe trunmons 68, this member 53 carries two trunnions 54 which engage intwo lugs 71 fixed on the lower portion of the oscillating platform shownat 52.

There has been shown at 74 a series of jacks which are actuated byhydraulic pressure applied from the top of the column. In the positionof rest, the pistons 75 of these jacks are located inside the chamber74, the end faces of the jacks being at the level of the outer face ofthe column foot. Under the action of hydraulic pressure ap plied fromthe surface of the water, and after the column foot has taken up itsposition correctly in the interior of the member 65, the column foot islocked by means of these pistons by causing the pistons to move forwardinto the housings 76.

The swivel-joint assembly 67, 68, 69, 70 and 71 permits movement in twodirections at right angles, that is to say the column is capable ofoscillating in any direction. The tractive pull of the oscillatingplatform on the base is transmitted through the intermediary of thepistons 75 of thejacks.

FIG. 9 shows diagrammatically the whole of the oscillating platform, thebase and the tubes which serve to anchor the said face. The sea-bed hasbeen shown at 77. At 78 there can be seen the tubes serving as ananchorage for the base 79. These tubes are kept under tension by thebuoyancy of the base which is in contact with the flanges fixed on theupper parts of the tubes. These tubes may be subjected to a few bendingstresses due to the movements of the base under the effect of the seacurrents, and to forces caused by the action of the sea on thearticulated platform. These displacements are however limited.

The base carries the column foot 80 which in turn supports the swiveljoint 81 which is fixed to the column 82 in the manner explained above.The column 82 is provided with floats 83 which on the one hand give it apositive buoyancy and on the other hand provide a restoring couple whichgives it stability about the vertical position.

Above the level of the sea, the column is equipped with a platform 84which can be used to support a drilling equipment or various productiondevices.

In the upper part of the column located above the surface of the sea,there may be arranged rooms intended for the staff and for the storageof products. The column may be equipped with tubes serving for thepassage of production lines. It may also be provided with storage spacefor the temporary storage of hydrocarbons.

FIG. 10 represents an oscillating platform with an anchored base, whichis employed in boring a well.

At 85, the column has been shown in the working position after it hasbeen anchored on the base by pivotal movement of the column, which isbrought to the place of working in a horizontal position, the pivotalmovement being effected by ballasting the column. There can be seen thefloats 86 described above, the fixing of the swivel joint 87, the columnfoot 89 and the support 90 rigidly fixed on the base 91, and theanchorage tube 92 for the base in the sea-bed, shown at 93. A drillingderrick is shown at 94; this is located on the platform carried by thecolumn together with the winch 95 and the group of sludge pumps 96 andmotors. It carries a train of drilling rods 97 which is first engaged ina tube 98 fixed on the oscillating platform. The tube 98 is coupled by aflexible connection 99 to one of the anchorage tubes of the base 91. Thetrain of drilling rods is engaged inside this tube 92, and a well 100can be bored with a diameter less than the internal diameter of thetubes 93. The corresponding shoulder is shown at 101 and the drillingtool is indicated at 102. The lengths of the tubes -92 may attainseveral hundred metres and the height of the column supporting theoscillating platform may be of the order of 100 to 400 metres.

FIG. 11 shows an assembly which can be utilized for the storage ofhydrocarbon products obtained from an underground field. The tubes 103passing inside the anchorage tubes of the base (anchorage tubes notshown) permit the exploitation of the fields shown at 104 and 105. Thesetubes terminate just above the base 106 in conventional well-heads 107and 108. These well-heads are connected by production conduits 109 toone or a number of flexible couplings such as 110, coaxial with thecolumn.

The tube 110 is connected to production conduits 111 fixed on thecolumn. These tubes are closed at the level of the oscillating platformby a series of valves 112 which enable the production taken from thefield to be directed either towards the various storage compartmentsinside the column, shown at 113, 114 and 115, or by a flexible conduit116 to a ship equipped for the transport of hydrocarbons, shown at 117.

The base 106 is substantially fixed, while on the other hand the column1s movable in rotation around the swivel joint. The lateral movement ofthe oscillating platform on the surface is of the order of a few metres.When the sea is not too rough, its oscillation of a few metres may beabsorbed by the movements of the production conduit 116 and the cable118 which enables the ship to be moored to the column.

What I claim is:

1. An off-shore structure comprising:

a plurality of piles projecting upward from and held in fixed positionsrelative to the bottom beneath a body of water;

a hollow base carried by said piles at a fixed distance from saidbottom, said base having a positive buoyancy which maintains said pilesunder tension;

a column having a positive buoyancy projecting upward from said basewith its upper end projecting above the surface of said body of water;

and a platform fixed to said upper end of said column;

said column being attached to said base by pivot means permitting saidcolumn and platform to swing as a unit above said base in at least twogenerally vertical planes about a single central point.

2. A structure as claimed in claim 1 in which the buoyancy of said baseis greater than the maximum load it is to be required to suport, andcomprising means for adjusting the buoyancy of said base.

3. A structure as claimed in claim 1 in which said base is formed withvertical openings through which said piles may be lowered from said baseand said piles carry stop means which prevent the upper ends of saidpiles from passing all the way through the base.

4. A structure as claimed in claim 1 in which at least some of saidpiles are hollow tubes adapted to guide a drilling string terminating ina drilling tool, so that said tool may be lowered through said tubes todrill holes in the bottom to receive said tubes.

5. A structure as claimed in claim 1 in which said 15 pivot means is adouble-trunnion swivel joint carried at the lower end of said column,said lower end being adapted to fit in a complementary recess in saidbase and carrying 8 a plurality of cylinders holding fluid operatedpistons, said structure comprising means for actuating said pistons fromsaid platform and projecting them beyond the ends of said cylinders intoregistering recesses in said base.

References Cited UNITED STATES PATENTS 3,118,408 1/1964 Knapp 6l--46.5 X3,355,899 12/1967 Koonce et a1. 6146.5 3,522,709 8/1970 Vilain 6146.53,525,388 8/1970 McClintock 61-46.54 X 3,524,323 8/1970 Miller 61--46.S

JACOB SHAPIRO, Primary Examiner US. Cl. X.R. 8-9; 1757

